These studies are directed towards obtaining a basic understanding of the structure and function of dentin matrix proteins. Detailed structural information of dentin matrix proteins and their interactions will be obtained. In this manner we hope to explain on a biochemical and molecular level, this tissue's functional significance. For this purpose, we wil differentiate this tissue into four compartments which are morphologically and biochemically different from each other and may represent the different developmental stages leading to mineralization of the matrix. These compartments include predentin proteins and three fractions of dentin proteins (non- mineralized fraction, EDTA extractable and non-extractable in mineralized fraction). The quantification of the collagen cross- link molecular distribution in these fractions of dentin frmo embryonic and postnatal bovine will be investigated. We shall compare these findings with other data obtained for other Type I collagen containing tissues in order to explore the structure- function relationships among various collagenous tissues that perform different functions in the body. The information from these studies will provide data concerning the stereospecificity of the chemical cross-linking reactions as well as the valuable insights into the azimuthal (angular) orientations of the collagen molecules in the fibrils. We shall also attempt to determine the structure and molecular locus of the phosphoprotein associated cross-links especially the putative intermolecular covalent cross-links that bind the dentin phosphoprotein to collagen, in the various compartments of dentin cited above. Covalent linkage between phosphoprotein and collagen might have an important role for mineralization mechanism. Cross-linked peptides will be isolated by chromatographic methods for tryptic digests of each compartment.